As long as the wash is "touchless", as others on the forum have written, it is not a problem. I would carry an "absorber" or some other drying towel to finish off the drying process, especially in the door jambs, trunk, etc. You won't get bug goop and road tar removed. If you keep a spray bottle in the trunk (that has a couple of drops of car soap in it) and pre-spray real well any bird droopings or other spots, you will increase what junk is removed during the wash.
Be sure and give your brakes a couple of good presses before you get on the road to dispel most of the water on the rotors. I also give the brakes another good pressing at around 40mph to finish off any water on them.
I wouldn't make this my regular method of keeping the car clean.
That being said....
Personally, I only take my Hondas through the any carwash. My BMW gets more attention than my dog. It's never seen a car wash and probably never will. It's never even seen a window squeegee. When I drive into a gas station, I like to see the shine on my paint/windows enough so that I need my sunglasses. If it's not perfect when I leave my driveway, I'm not very happy. I even carry a quick detailer in my trunk. So if you see a guy in a parking lot somewhere wiping down his car, it's probably me.
My goal is to be able keep my car with such a shine that it can be driven onto any BMW showroom at any time on any day and no one know the difference (including the rims/tires).
But that's just me....
Read through the FAQ's and the Detailing forum for more info.
to the forum. Keep us updated on your new ride. We look forward to hearing how things are going with your bimmer. Post some pics. We all like pics.